There's currently no online database that I know of that is controlled by, say, the government, and says which books have been published online and by whom and where and with valid links to each. It'd be nice to have, but until something like that exists, buying from Amazon (or wherever) is still a crapshoot to a certain (rather small) extent.

My problem with this is that people assume that since it is on Amazon, it is OK. And that is wrong.

I've been in train stations where they keep repeating that you shouldn't leave your luggage unattended. Project Gutenberg tells people to check if the books are in public domain in their countries. Amazon could place a banner saying that people should check if the books are legit.